I also started HRT at 21, I inherited my family body shape for women, my mother and I have the same body shape.. wider hip with a bum to match... (Hour glass)
I dont know how much it widened by..but the dresses I wore before HRT, do not fit me at all, I cant even get some of them even close to over my bum.
Body shape to determined by genetics. We must not fall into the same trap cis-women do, by thinking there is only one acceptable body shape.. Women come in all shapes and sizes.. I use to know a girl (cis-girl) who had virtually no body shape... I actually have a way more shape than she does.
I wish I could have started HRT at 12, I would have been able to be a teenage girl.. At 12, I was only starting to wish I could be a girl.. I would have never believed someone, if they told the 12 year old me, I would grow into a woman..